U.S. patent application number 12/727805 was filed with the patent office on 2010-09-23 for reducing channel overhead in a wireless coexistence network.
This patent application is currently assigned to TEXAS INSTRUMENTS INCORPORATED. Invention is credited to Xiaolin Lu, Yanjun Sun, Ariton E. Xhafa.
Application Number | 20100238807 12/727805 |
Document ID | / |
Family ID | 42737512 |
Filed Date | 2010-09-23 |
United States Patent
Application |
20100238807 |
Kind Code |
A1 |
Xhafa; Ariton E. ; et
al. |
September 23, 2010 |
REDUCING CHANNEL OVERHEAD IN A WIRELESS COEXISTENCE NETWORK
Abstract
A system composed of a device configured to communicate, using a
first wireless protocol, with a node. The system also comprises a
processor coupled to the device and configured to determine whether
the node operates in a coexistence mode. If the processor
determines that the node operates in a coexistence mode then, as a
result, the processor determines when the node operates in the
first wireless protocol and communicates, by way of the device and
without solicitation from the node, with the node when the node
operates in the first wireless protocol.
Inventors: |
Xhafa; Ariton E.; (Plano,
TX) ; Sun; Yanjun; (Richardson, TX) ; Lu;
Xiaolin; (Plano, TX) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
US
|
Assignee: |
TEXAS INSTRUMENTS
INCORPORATED
Dallas
TX
|
Family ID: |
42737512 |
Appl. No.: |
12/727805 |
Filed: |
March 19, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61161447 |
Mar 19, 2009 |
|
|
|
Current U.S.
Class: |
370/241 ;
370/328 |
Current CPC
Class: |
H04W 88/06 20130101;
H04W 72/1215 20130101 |
Class at
Publication: |
370/241 ;
370/328 |
International
Class: |
H04L 12/26 20060101
H04L012/26; H04W 4/00 20090101 H04W004/00 |
Claims
1. A system comprising: a device configured to communicate, using a
first wireless protocol, with a node; and a processor coupled to
the device and configured to determine whether the node operates in
a coexistence mode; wherein, if the processor determines that the
node operates in a coexistence mode then, as a result, the
processor: determines when the node operates in the first wireless
protocol; and communicates, by way of the device and without
solicitation from the node, with the node when the node operates in
the first wireless protocol.
2. The system of claim 1 wherein if the processor determines that
the node operates in a coexistence mode then, as a result, the
processor further determines that the node periodically operates in
at least the first wireless protocol and a second wireless
protocol.
3. The system of claim 2 wherein if the processor determines that
the node operates in a coexistence mode then, as a result, the
processor further receives an indication of when the node ceases to
operate in the second wireless protocol.
4. The system of claim 2 wherein if the processor determines that
the node operates in a coexistence mode then, as a result, the
processor further determines when the node begins to operate in the
second wireless protocol.
5. The system of claim 1 wherein if the processor receives an
indication that the processor has incorrectly determined when the
node operates in the first wireless protocol then, as a result, the
processor communicates, by way of the device, with the node in
response to solicitation from the node.
6. The system of claim 1 wherein if the processor determines that
the node operates in a coexistence mode then, as a result, the
processor further communicates with the node only when the node
operates in the first wireless protocol.
7. The system of claim 1 wherein if the processor receives an
indication that the node is available for a data transmission and
the processor subsequently receives a request for network silence,
then, as a result, the processor determines that the node is
operating in a coexistence mode.
8. A system comprising: a device configured to communicate with an
access point using a first wireless protocol; and a processor
coupled to the device and configured to operate the device in a
coexistence mode; wherein, if the processor receives an
acknowledgement from the access point that the processor operates
in the coexistence mode, then the processor receives data from the
access point, by way of the device and without solicitation from
the processor.
9. The system of claim 8 wherein the device is configured to
communicate with a second device using a second wireless
protocol.
10. The system of claim 9 wherein if the processor operates the
device in a coexistence mode then the device periodically operates
in at least the first wireless protocol and the second wireless
protocol.
11. The system of claim 8 wherein if the processor receives an
acknowledgement from the access point then the processor
communicates with the access point only when the device operates in
the first wireless protocol.
12. The system of claim 8 wherein the device is configured to
communicate with a node and wherein if the processor determines
that the node operates in a coexistence mode then, as a result, the
processor: determines when the node operates in the first wireless
protocol; and communicates, by way of the device and without
solicitation, with the node only when the node operates in the
first wireless protocol.
13. A method comprising: determining, by an access point, that a
node is operating in a coexistence mode; determining, by the access
point, when the node is operating in either of a first wireless
protocol or a second wireless protocol; and communicating, by the
access point and without solicitation from the node, with the node
only when the node is operating in the first wireless protocol.
14. The method of claim 13 further comprising receiving, by the
access point, an indication that the access point has incorrectly
determined when the node is operating in the first wireless
protocol and second wireless protocol and, as a result,
communicating with the node using solicitation from the node.
15. The method of claim 13 wherein determining when the node is
operating in each of a first wireless protocol and a second
wireless protocol further comprises determining that the node is
periodically operating in at least the first wireless protocol and
a second wireless protocol.
16. The method of claim 15 further comprising receiving an
indication of when the node ceases to operate in the second
wireless protocol.
17. The method of claim 15 further comprising determining when the
node begins to operate in the second wireless protocol.
18. The method of claim 13 wherein determining that the node is
operating in a coexistence mode further comprises receiving an
indication that the node is available for a data transmission
followed by receiving a request for network silence.
19. A method comprising: sending, by a node, an indication that the
node is operating in a coexistence mode; receiving, by the node, an
acknowledgement from an access point that the node is operating in
a coexistence mode; and communicating, by the node and without
solicitation from the node, with the access point.
20. The method of claim 19 wherein sending an indication further
comprises sending an indication that the node is periodically
operating in at least a first wireless protocol and a second
wireless protocol.
21. The method of claim 20 wherein communicating further comprises
communicating only when the node is operating in the first wireless
protocol.
22. The method of claim 20 further comprising communicating with a
second device only when the node is operating in the second
wireless protocol.
23. The method of claim 19 further comprising: receiving, by the
node, an indication that a second node is operating in a
coexistence mode; determining, by the node, when the second node is
operating in each of a first wireless protocol and a second
wireless protocol; communicating, by the node and without
solicitation, with the second node only when the second node is
operating in the first wireless protocol.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority to U.S. Provisional
Patent Application No. 61/161,447, filed on Mar. 19, 2009 (Attorney
Docket No. TI-67863), which is hereby incorporated herein by
reference.
BACKGROUND
[0002] Mobile devices are able to access multiple networks using
wireless protocols operating at close frequency bands. However,
when a single device utilizes two or more wireless protocols, the
proximity of the frequency bands may lead to interference between
data sent using the protocols, which may cause problems with the
simultaneous operation of the protocols. Specifically, out-of-band
transmissions using one protocol may saturate a receiver using a
second protocol, effectively blocking transmissions using the
second protocol. Thus, coexistence of multiple protocols on a
single device often is problematic.
SUMMARY
[0003] The problems noted above are solved in large part by a
system comprising a device configured to communicate, using a first
wireless protocol, with a node. The system also comprises a
processor coupled to the device and configured to determine whether
the node operates in a coexistence mode. If the processor
determines that the node operates in a coexistence mode then, as a
result, the processor determines when the node operates in the
first wireless protocol. The processor communicates, by way of the
device and without solicitation from the node, with the node when
the node operates in the first wireless protocol.
[0004] Furthermore, the problems noted above are solved in large
part by a system comprising a device configured to communicate with
an access point using a first wireless protocol. The system also
comprises a processor coupled to the device and configured to
operate the device in a coexistence mode. If the processor receives
an acknowledgement from the access point that the processor
operates in the coexistence mode, the processor receives data from
the access point, by way of the device and without solicitation
from the processor.
[0005] Still further, the problems noted above are solved in large
part by a method comprising determining, by an access point, that a
node is operating in a coexistence mode. The method also comprises
determining, by the access point, when the node is operating in
either of a first wireless protocol or a second wireless protocol.
The method further comprises communicating, by the access point and
without solicitation from the node, with the node only when the
node is operating in the first wireless protocol.
[0006] Finally, the problems noted above are solved in large part
by a method comprising sending, by a node, an indication that the
node is operating in a coexistence mode. The method also comprises
receiving, by the node, an acknowledgement from an access point
that the node is operating in a coexistence mode. The method
further comprises communicating, by the node and without
solicitation from the node, with the access point.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a detailed description of exemplary embodiments of the
invention, reference will now be made to the accompanying drawings
in which:
[0008] FIG. 1 shows the transmission of a Power Save Poll (PSPoll)
frame for communication between a node and an access point in
accordance with various embodiments;
[0009] FIG. 2 shows the transmission of a Clear to Send to Self
(CTS2Self) frame for communication between a node and an access
point in accordance with various embodiments;
[0010] FIG. 3 shows a block diagram of an illustrative system in
accordance with various embodiments;
[0011] FIG. 4 shows the transmission of Request to Send/Clear to
Send (RTS/CTS) messages in accordance with various embodiments;
[0012] FIG. 5 shows the transmission of a data frame in accordance
with various embodiments;
[0013] FIG. 6 shows a flow diagram of an illustrative method in
accordance with various embodiments; and
[0014] FIG. 7 shows a flow diagram of another illustrative method
in accordance with various embodiments.
NOTATION AND NOMENCLATURE
[0015] Certain terms are used throughout the following description
and claims to refer to particular system components. As one skilled
in the art will appreciate, companies may refer to a component by
different names. This document does not intend to distinguish
between components that differ in name but not function. In the
following discussion and in the claims, the terms "including" and
"comprising" are used in an open-ended fashion, and thus should be
interpreted to mean "including, but not limited to . . . ." Also,
the term "couple" or "couples" is intended to mean either an
indirect, direct, optical or wireless electrical connection. Thus,
if a first device couples to a second device, that connection may
be through a direct electrical connection, through an indirect
electrical connection via other devices and connections, through an
optical electrical connection, or through a wireless connection.
The term "WLAN" refers to a wireless local area network, for
example, in the IEEE 802.11 protocol. The term BT refers to the
Bluetooth.RTM. wireless protocol. The term "U-APSD" refers to an
unscheduled automatic power-saving delivery mode, where certain
circuits are turned off when not needed for various computing
functions. The term "PSPoll" refers to a power save poll frame,
which may be used to alert a node of a network that the node
sending the frame is available for data transmission. The term "AP"
refers to an access point, which may be a device that facilitates
wireless communication in a wireless network. The term "CTS2Self"
refers to a frame, which may reserve a period of network silence.
The terms "RTS" and "CTS" refer to Request to Send and Clear to
Send messages, respectively. The term "ACK" refers to an
acknowledgement message.
DETAILED DESCRIPTION
[0016] The following discussion is directed to various embodiments
of the invention. Although one or more of these embodiments may be
preferred, the embodiments disclosed should not be interpreted, or
otherwise used, as limiting the scope of the disclosure, including
the claims. In addition, one skilled in the art will understand
that the following description has broad application, and the
discussion of any embodiment is meant only to be exemplary of that
embodiment, and not intended to intimate that the scope of the
disclosure, including the claims, is limited to that
embodiment.
[0017] Time multiplexed switching between protocols is utilized to
facilitate coexistence of multiple wireless technologies at a
single node (e.g., a computer, PDA, smart phone). For example, in
the case of WLAN and Bluetooth.RTM. (BT) coexistence, BT voice
calls take priority over other data traffic flows using WLAN.
During the time periods in which the node operates in BT mode, the
WLAN portion operates in an unscheduled automatic power-saving
delivery (U-APSD) mode. In the U-APSD mode, circuitry that is
required only for WLAN mode operation may be turned off, so that
power may be conserved when the WLAN mode is not active (i.e.,
during BT operation). During the time in which the node operates in
WLAN mode, the node may indicate that it is ready to receive a data
frame by sending a trigger frame to an access point (AP). The
trigger frame may be, for example, a Power Save Poll (PSPoll) frame
in the IEEE 802.11 standard (all 802.11 protocols are hereby
incorporated herein by reference).
[0018] If the AP sends a data frame addressed to the node within
the WLAN mode time period and expects a subsequent acknowledgment
signal but the node is not able to reply with such an
acknowledgement signal, a rate-fall back mechanism is triggered by
the AP. Alternatively, if the AP sends a data frame outside of the
WLAN mode time period, the rate-fall back mechanism is triggered.
In either situation, this rate-fall back mechanism reduces the
transmission rate used to send data frames from the AP to the node,
causing the data frames transmitted to occupy longer time
intervals. This, in turn, may lead to conflict with the use of the
medium by the BT mode. As a result, the performance of the node in
both BT and WLAN modes deteriorates. Such deterioration may be
referred to as the "avalanche effect."
[0019] FIG. 1 shows the transmission of a PSPoll frame 102 by a
node operating in a coexistence mode (i.e., utilizing multiple
wireless technologies, in this case BT and WLAN). Additionally, an
AP sends an acknowledgement frame 104 and later a data frame 106.
Although the node operates in a coexistence mode, the AP only
operates using one wireless technology (e.g., WLAN). The node
responds with an acknowledgement 108. Typically, the node sends the
PSPoll frame 102 to an AP immediately upon switching to WLAN mode
112 to increase the chances that the AP will send a data frame
during the WLAN mode time period and not during the following BT
mode 114. However, the AP may not be able to send the data frame
106 during the WLAN mode time period 112 if the network is
congested. In the case where the node expects a data frame but does
not receive one before the end of the WLAN mode time period, the
node may send a frame that reserves the network for a period of
time, thus avoiding a transfer of data from the AP during the
impending BT mode time period 114. In some instances, this frame
may take the form of a CTS2Self frame. FIG. 2 shows the
transmission of a CTS2Self frame 206 to protect from the avalanche
effect. FIG. 2 further shows the transmission of a PSPoll frame 202
and an acknowledgement 204, similar to FIG. 1. To ensure that no
transmission to the node takes place during the BT mode time period
212, the time period 211 reserved by the node is the sum of the
time remaining in the WLAN mode time period 210 and the time
scheduled to be occupied by the impending BT mode time period 212.
In this way, the use of the PSPoll 202 and CTS2Self 206 frames
provide the node with the ability to solicit communication from the
AP during the WLAN mode time period 210 and avoid the avalanche
effect.
[0020] Although sending the CTS2Self frame prevents the avalanche
effect, it also requests a period of network silence, thus
silencing other nodes in the network from transmitting or receiving
data frames. This may result in a negative impact on the overall
network performance.
[0021] Various embodiments disclosed herein provide protection from
the avalanche effect without the negative network performance
impacts associated with the repeated use of CTS2Self frames.
Specifically, in some such embodiments, the WLAN and BT modes may
be periodic in nature--for example, when BT mode is being used for
voice traffic. Such periodicity makes it possible for the AP to
predict or estimate when the BT mode will occur in each period
(e.g., based on information received from the node in the PSPoll or
CTS2Self frames). If the AP successfully predicts, estimates or
otherwise determines when the BT mode time period will occur in
each period and communicates this information to the node, the node
may cease the transmission of the PSPoll frame, CTS2Self frame or
both, because the AP no longer requires the information provided in
the PSPoll and CTS2Self frames to avoid transmitting to the node
during the BT mode time period. The communication from the AP to
the node, indicating successful determination of when the BT mode
time period will occur, may take the form of an explicit indication
or, in alternative embodiments, may be implicitly determined by the
node. Thus, communication between the AP and the node may continue
without the use of PSPoll and CTS2Self frames (i.e., in an
unsolicited manner). The overhead required by the PSPoll and
CTS2Self frames may be used for additional data transmissions,
thereby positively impacting overall network performance.
[0022] FIG. 3 shows a block diagram of an illustrative system 300
in accordance with various embodiments. System 300 may comprise a
wireless network in which at least some nodes are configured to
operate in a coexistence mode. That is, at least some nodes are
configured to operate using more than one wireless communication
protocol (e.g., WLAN, BT). In some embodiments, the coexistence
mode is facilitated by time-multiplexing the wireless technologies
in a periodic manner.
[0023] As shown, system 300 comprises an AP 302 coupled to nodes
308 and 318. The AP 302 comprises a device 304 coupled to a
processor 306. The device 304 may be used for wireless
communication and may comprise, for example, a wireless transceiver
and/or antenna. The node 308 comprises a device 310 coupled to a
processor 312. Similar to the device 304, the device 310 may be
used for wireless communication. The node 308 also couples to a
device 316 by way of device 310. In some embodiments, the device
316 may be a BT-equipped device. The node 318 comprises a device
320 coupled to a processor 322. Similar to devices 304 and 310, the
device 320 may be used for wireless communication. The nodes 308
and 318 couple to the AP 302 through device 304, by way of devices
310 and 320, respectively. The system 300 is shown as an exemplary
embodiment; one skilled in the art would understand that other
embodiments may include more than one AP 302, more than one of each
node 308 and 318, or more than one device 316.
[0024] In accordance with various embodiments, devices 304, 310,
320 are configured to communicate using one or more wireless
communication standards. For example, device 304 and device 320 may
be configured to communicate using a first wireless protocol (e.g.,
WLAN) by utilizing first protocol logics 307 and 324, respectively.
The first protocol logics 307 and 324 serve to facilitate, by way
of processors 306 and 322, encoding and decoding of signals in the
first wireless protocol sent or received by devices 304 and 320.
Device 310 may be configured to communicate using both a first
wireless protocol (e.g., WLAN) as well as a second wireless
protocol (e.g., BT) by utilizing a first protocol logic 314a and a
second protocol logic 314b, respectively. The first and second
protocol logics 314a, 314b operate similarly to the first protocol
logics 307 and 324 above. However, each protocol logic 314a, 314b
serves to facilitate, by way of processor 312, encoding and
decoding of signals in either the first wireless protocol or the
second wireless protocol sent or received by device 310. Device 316
may be configured to communicate using only a second wireless
protocol (e.g., BT) by similarly utilizing a second protocol logic
317. Thus, device 310 may enable node 308 to communicate with AP
302 through device 304 using WLAN protocol while also enabling node
308 to communicate with device 316 using BT protocol.
[0025] In accordance with various embodiments, node 308 may be
configured to operate in a coexistence mode, where both wireless
protocol logics 314a, 314b are utilized in a periodic manner. As
discussed above, such a coexistence mode may be accomplished by
time-multiplexing the wireless protocols. For example, node 308 may
utilize the first protocol logic 314a in a first sub-period (e.g.,
"WLAN mode") and the second logic 314b in a second sub-period
(e.g., "BT mode"). As a result, during each period of a periodic
communication, the node 308 may engage in both WLAN and BT
transmissions.
[0026] In accordance with various embodiments, AP 302 may determine
that node 308 is operating in a coexistence mode. More
specifically, and as discussed above, node 308 may communicate with
AP 302 using PSPoll and CTS2Self frames. In an illustrative
embodiment, node 308 operates in WLAN mode and sends a PSPoll frame
to AP 302 and during the same WLAN mode time period sends a
CTS2Self frame to AP 302. No frames follow the CTS2Self frame. FIG.
2, element 210 shows such a WLAN mode time period. Such a sequence
may cause AP 302 to determine that node 308 is operating in a
coexistence mode. In an alternative embodiment, AP 302 may send a
data frame to node 308 and expect a reply or acknowledgement. If AP
302 sends the data frame while node 308 is operating in BT mode,
then node 308 will not reply or acknowledge the data frame.
Additionally, AP 302 may send the data frame while node 308 is
operating in WLAN mode; however, node 308 may not have enough time
to send a reply or acknowledgement before switching to BT mode.
Thus, failing to receive a reply or acknowledgement from node 308
after sending a data frame may also cause AP 302 to determine that
node 308 is operating in a coexistence mode.
[0027] Again referring to FIG. 2, in some embodiments, the CTS2Self
frame 206 is transmitted during WLAN mode 210 and indicates a
duration of WLAN silence 211, which includes the BT mode 212. Thus,
the CTS2Self frame 206 indicates when the upcoming BT mode 212
stops (time 213), thereby indicating when node 308 switches back to
WLAN mode 214. However, the CTS2Self frame may not indicate when
node 308 switches to the upcoming BT mode (time 215). AP 302 may
predict when the node 308 will switch to the upcoming BT mode (time
215) by utilizing the duration of WLAN silence 211 in combination
with knowledge of the duration of BT mode 212. For example, if node
308 operates in a coexistence mode to facilitate BT voice traffic
during BT mode, BT voice traffic may occupy a 1.25 ms frame during
each period. In this example, AP 302 may be aware that node 308
commonly uses BT modes 212, 216 to facilitate BT voice traffic, and
thus deduct 1.25 ms from the endpoint of the duration of WLAN
silence (time 213) to predict when node 308 will switch to the
upcoming BT mode (time 215). Additionally, because BT voice traffic
is periodic in nature, AP 302 may leverage the knowledge of the
upcoming BT mode 212 to estimate when BT modes in future periods
216 will occur. This prediction mechanism may be extended to any
traffic that is periodic in nature and it should be appreciated
that certain other traffic may have a duration of more or less than
1.25 ms.
[0028] Referring back to FIG. 3, when the BT mode duration has been
predicted by AP 302, AP 302 may send an acknowledgement to node 308
that AP 302 recognizes node 308 to be operating in a coexistence
mode and that AP 302 has knowledge of when node 308 will be
operating in WLAN mode and BT mode. Thus, AP 302 will only transmit
data to node 308 during WLAN mode, which avoids the avalanche
effect, and node 308 may cease to transmit PSPoll and CTS2Self
frames. Thus, once AP 302 determines that node 308 is operating in
a coexistence mode, the periodic nature of the coexistence mode
allows AP 302 and node 308 to communicate without solicitation
(i.e., without use of PSPoll and/or CTS2Self frames).
[0029] In accordance with various embodiments, AP 302 may
acknowledge that node 308 is operating in a coexistence mode by
sending a Request to Send (RTS) message to node 308, prior to
sending a data frame to node 308. Node 308 may acknowledge receipt
of the RTS by sending a Clear to Send (CTS) message. Node 308 may
also cease to transmit PSPoll and CTS2Self frames; thus,
communication between AP 302 and node 308 occurs unsolicited. FIG.
4 shows the transmission of an RTS 402 by the AP 302 and a CTS 404
by node 308. Additionally, a data frame 406 is sent by AP 302 and
an acknowledgement 408 is sent by node 308. If node 308 receives an
RTS 402 from AP 302, node 308 may interpret the RTS 402 as
signifying that AP 302 is aware that node 308 is operating in a
coexistence mode. In other words, the receipt by node 308 of an RTS
402 from AP 302 serves as an acknowledgement that node 308 is
operating in a coexistence mode.
[0030] Typically, AP 302 will transmit the RTS 402 such that there
is sufficient time before node 308 switches to BT mode for node 308
to send a CTS 404 and for AP 302 to transmit a data frame 406 and
receive an ACK 408 from node 308. However, conditions such as
non-periodic traffic may cause the BT mode to be longer or shorter
in duration than AP 302 predicted, and thus the prediction of when
node 308 will switch to BT mode may be flawed. In such a situation,
node 308, upon receiving the RTS 402, may determine that there is
insufficient time remaining before switching to BT mode to send a
CTS to AP 302, receive data from AP 302 and send an ACK to AP 302,
and thus will resume sending PSPoll and CTS2Self frames to AP 302.
AP 302 may observe these frames from node 308 and, as above,
predict when BT modes will occur.
[0031] In alternative embodiments, a BT mode mis-prediction by AP
302 may be handled differently. For example, if AP 302 has already
acknowledged node 308 in a coexistence mode through the RTS-CTS
mechanism described above, and AP 302 predicts that node 308 should
be in WLAN mode, but node 308 is in BT mode because of non-periodic
BT traffic, AP 302 is unaware that node 308 is in BT mode and
attempts to transmit data to node 308, where the transmission of
data is not preceded by the RTS-CTS mechanism. Node 308 will not
respond immediately, since node 308 is operating in BT mode. As
discussed above, node 308 failing to respond to a data frame
transmission will cause AP 302 to trigger a rate-fall back
mechanism. Upon determining that the transmission rate has been
reduced, node 308 may determine that there has been a BT mode
mis-prediction and resume sending PSPoll and CTS2Self frames. AP
302 may observe these frames from node 308 and, as above, predict
when BT modes will occur.
[0032] In some embodiments, AP 302 may facilitate unsolicited
communications by sending data frames with a "more-data" bit set to
zero. Setting the more-data bit to zero causes node 308 not to
transmit a PSPoll frame, which would normally be used to inform AP
302 that node 308 is ready to receive more data. FIG. 5 shows AP
302 sending a data frame 502 with the "more data" bit 503 set to
zero. Thus, AP 302 may also indicate a BT mode mis-prediction by
setting the more-data bit 503 to one, since this will cause node
308 to transmit PSPoll and CTS2Self frames. For example, if AP 302
sends a data frame 502 with the more-data bit 503 set to zero, AP
302 expects to receive an ACK 504 from node 308. If no ACK 504 is
received, AP 302 determines that a BT mode mis-prediction has
occurred and sends a data frame 502 with the more-data bit 503 set
to one, indicating the BT mode mis-prediction to node 308 and
triggering the transmission by node 308 of PSPoll and CTS2Self
frames. AP 302 may observe these frames from node 308 and, as
above, predict when BT modes will occur.
[0033] In accordance with various embodiments, AP 302 may detect
when node 308 stops using BT mode. In this situation, the AP 302
may stop communicating with node 308 as if it is operating in a
coexistence mode. AP 302 may treat the reception of a WLAN
transmission from node 308 during the predicted BT mode as an
indication of the termination of BT traffic at node 308.
Alternatively, AP 302 may transmit an RTS to node 308 before the
predicted BT mode, so that node 308 may only send a CTS when BT
mode is not under use anymore. If a CTS is received early (i.e.,
during what would normally be the BT mode), AP 302 may deduce that
node 308 is no longer operating in a coexistence mode. AP 302 may
also send a data frame that overlaps with the BT mode to observe if
the BT traffic at node 308 is still active. Reception of an ACK
from node 308 indicates that BT traffic is not active and data may
be transmitted to node 308 at any time. Thus, AP 302 realizes when
node 308 no longer operates in a coexistence mode, and may take
advantage of the BT mode time every period to communicate with the
node 308. This positively impacts the bandwidth availability
between node 308 and AP 302.
[0034] In accordance with various embodiments, functionality of AP
302 and node 308 may be combined in a single device. One skilled in
the art would understand that such combination could facilitate
creation of ad hoc networks where nodes may assume the role of APs
in relation to other nodes in the network. In this way, node 308
may function as a "soft AP" for node 318, for example.
[0035] FIG. 6 shows a method 600 in accordance with various
embodiments. The method begins when an AP 302 determines that a
node 308 is operating in a coexistence mode (block 602). As above,
node 308 operates in WLAN mode and sends a PSPoll frame to AP 302
and during the same WLAN mode time period sends a CTS2Self frame to
AP 302. No frames follow the CTS2Self frame. FIG. 2, element 210
shows such a WLAN mode time period. Such a sequence may cause AP
302 to determine that node 308 is operating in a coexistence mode.
In an alternative embodiment, AP 302 may send a data frame to node
308 and expect a reply or acknowledgement. If AP 302 sends the data
frame while node 308 is operating in BT mode, then node 308 will
not reply or acknowledge the data frame. Additionally, AP 302 may
send the data frame while node 308 is operating in WLAN mode;
however, node 308 may not have enough time to send a reply or
acknowledgement before switching to BT mode. Thus, failing to
receive a reply or acknowledgement from node 308 after sending a
data frame may also cause AP 302 to determine that node 308 is
operating in a coexistence mode.
[0036] The method then proceeds to the AP 302 determining when the
node 308 is operating in a first wireless protocol (e.g. WLAN) and
a second wireless protocol (e.g., BT) (block 604). Referring back
to FIGS. 2 and 3 as an example, if node 308 operates in a
coexistence mode to facilitate BT voice traffic during BT mode, BT
voice traffic may occupy a 1.25 ms frame during each period. In
this example, AP 302 may be aware that node 308 commonly uses BT
modes 212, 216 to facilitate BT voice traffic, and thus deduct 1.25
ms from the endpoint of the duration of WLAN silence (time 213) to
predict when node 308 will switch to the upcoming BT mode (time
215). Additionally, because BT voice traffic is periodic in nature,
AP 302 may leverage the knowledge of the upcoming BT mode 212 to
estimate when BT modes in future periods 216 will occur. This
prediction mechanism may be extended to any traffic that is
periodic in nature and it should be appreciated that certain other
traffic may have a duration of more or less than 1.25 ms.
[0037] If the node 308 is operating in the first wireless protocol
(decision block 606), the method proceeds to the AP 302
communicating with the node 308 without solicitation from the node
(block 608) (i.e., without PSPoll frame, CTS2Self frame or both)
and the method ends. Such unsolicited communication may employ the
RTS-CTS mechanism as in FIG. 4 and described above, or setting the
"more data" bit 503 to zero as in FIG. 5 and described above.
However, if the node 308 is not operating in WLAN mode (decision
block 606), the method waits until the node 308 is operating in the
first wireless protocol.
[0038] FIG. 7 shows a method 700 in accordance with various
embodiments. The method begins when a node 308 sends an indication
that it is operating in a coexistence mode (block 702). As above,
node 308 operates in WLAN mode and sends a PSPoll frame and during
the same WLAN mode time period sends a CTS2Self frame. No frames
follow the CTS2Self frame. FIG. 2, element 210 shows such a WLAN
mode time period. Such a sequence may indicate that node 308 is
operating in a coexistence mode. The method then proceeds to the
node receiving an acknowledgement from an AP 302 that the node 308
is operating in a coexistence mode (block 704). In some
embodiments, the node 308 receiving an RTS message from AP 302
serves as an acknowledgement of node 308 operating in a coexistence
mode, as in FIG. 4 and described above. The method continues with
the node 308 communicating with the AP 302 without solicitation
from the node 308 (block 706) and the method ends. Such unsolicited
communication may employ the RTS-CTS mechanism as in FIG. 4 and
described above, or setting the "more data" bit 503 to zero as in
FIG. 5 and described above.
[0039] The above discussion is meant to be illustrative of the
principles and various embodiments of the present invention.
Numerous variations and modifications will become apparent to those
skilled in the art once the above disclosure is fully appreciated.
It is intended that the following claims be interpreted to embrace
all such variations and modifications.
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